Withstanding Hurricanes

Hurricane season began June 1, and NOAA’s annual hurricane forecast for the Atlantic, Caribbean and Gulf of Mexico calls for 12 to 18 named storms, with six to 10 becoming hurricanes. The agency predicts up to six major hurricanes, with wind speeds above 111 mph.

Hurricanes are some of the most devastating weather events to affect the United States, with nationwide damages averaging $36 billion a year since 2000. This is due, in large part, to the large proportion of communities along the seaboard; nearly half of the country’s total population lives within 50 miles of the coastline. Costs associated with hurricane damage have a greater impact on Florida with its 1,200 miles of coastline.

Florida Sea Grant has funded and is currently funding research projects aimed at mitigating the effects of hurricanes by reducing the amount of damage they inflict on residential and commercial buildings. The outcome of these projects will lead to better building codes and practices for the design of hurricane-resistant buildings in coastal areas.

Arindam Chowdhury, a Florida International University assistant professor in the Department of Civil and Environmental Engineering received Florida Sea Grant funding to evaluate the capacity of buildings to withstand hurricane winds and rain using FIU’s full-scale hurricane simulator, the Wall of Wind (WoW).

Composed of six large fans that can generate sustained winds up to 130 mph, the WoW is capable of simulating a Category 3 hurricane. The WoW test facility also includes a water-injection system that is used to simulate the horizontal rain associated with these severe storms.

Chowdhury and his team have successfully used the WoW to estimate the effects of hurricane-induced wind and rain on residential building envelopes (a building envelope is what physically separates the interior and exterior of a building and includes the foundation, roof, walls, doors and windows). Their experiments have identified how envelope components fail and have allowed Chowdhury to develop strategies and new building products to retrofit existing construction components to address failure “hot spots.”

One such strategy is using a type of fiberglass tape in place of traditional hardware, such as nails, screws or bolts, in construction. Chowdhury and his team found that the traditional hardware used to connect building components is intrusive and weakens the building’s ability to stand up to a hurricane by creating holes and making a path for water to enter. However, if non-intrusive Glass Fiber Reinforced Polymer (GFRP) and epoxy is used to connect components, the structure is not weakened and there is no path for water to enter. WoW testing showed that the GFRP connections were able to withstand higher winds than traditional hardware, and exceeded the minimum requirement specified by the Florida Building Code.

In a similar study, Florida Sea Grant is funding David Prevatt, a University of Florida assistant professor in the Department of Civil and Coastal Engineering, to evaluate the use of closed-cell spray-applied polyurethane foam (ccSPF) to increase wind resistance of wood roof decks while simultaneously providing a secondary water barrier.

The results of the first phase of Prevatt’s research shows that roof panels retrofitted with ccSPF are approximately five times more wind resistant than those that were not retrofitted. The second phase of the study is now underway with several experiments investigating how moisture is accumulated and transported through ccSPF retrofitted roofs. Prevatt’s research is anticipated to lead to improved guidelines for using ccSPF as a structural retrofit and as insulation for residential wood roof decks in hot, humid regions.